Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1338097
The present invention concerns a method in a drying
group or groups provided with a single-wire draw in a
multi-cylinder dryer of a paper machine for supporting a
web, the multi-cylinder dryer comprising drying
cylinders heated by means of steam or equivalent, and
the web being pressed by the drying wire directly
against the cylinder faces of the drying cylinders.
Furthermore, the multi-cylinder dryer comprises leading
cylinders or rolls, on which the web remains outside of
the drying wire.
Further, the present invention concerns a device
which is applied in the area of a single-wire draw in a
multi-cylinder dryer of a paper machine, this dryer
comprising a line of heated drying cylinders,
preferably upper cylinders, and a line of leading
cylinders or rolls, the web running between these lines
while being supported by a drying wire, e.g. a felt, so
that the web is pressed by the drying wire on the heated
drying cylinders into direct contact with the heated
face of these drying cylinders, while the web is
situated on an outer face of the drying wire over the
leading cylinders or rolls.
The present invention also concerns a cylinder
used in the draw of a paper web.
A problem in the case of leading rolls of single-
wire groups in a drying section of a paper machine, has
been making a paper web adhere to the wire on the lower
face of the cylinder. On the lower cylinders or leading
rolls, the web runs as a topmost layer, while the wire
remains between the web and an outer face of the leading
cylinder or roll. This problem does not occur in the
case of the other rolls in a single-wire group, since
the paper web runs between the wire and the mantle face
of the cylinder.
Attempts have been made to solve this problem by
utilizing suction rolls. A suction roll is quite
,~L
: j Ij ij,
13~8'~ l
expensive, with a suction box requiring inner sealing
ribs which tend to become worn. When the sealing ribs
operate dry, the wearing is even more extensive.
Negative pressure is applied through the suction
box of a suction roll to a vacuum block inside the
cylinder. This vacuum block is placed in a lower half
of the cylinder in the case of the lower cylinders in a
single-wire group. Through the negative pressure
applied to this block, suction is expressly applied to
lo a part of the cylinder face in which the paper web
tends to become detached. Through bores in the mantle,
negative pressure is applied through the felt to the
paper web, which thereby adheres to the felt face.
A solution in the prior art for this problem of
the paper web tending to become detached, is also known
in which an arrangement in accordance with Valmet U.S.
Patent No. 4,693,784 is used. In the noted Uno-Vac*
system, a type of suction box is used in which no
wearing seals placed against the inner face of the roll
mantle are used. In this solution, a high-velocity air
flow is applied to the proximity of the edge of the
suction box and the mobile mantle face. This air flow
generates a suction flow from the interior of the box,
which thereby prevents flow of air through the edge
area in the opposite direction into the space of nega-
tive pressure. A negative pressure is applied to the
interior of the suction box and is transferred through
the bores in the mantle to the web face. The high cost
of construction of the equipment is considered a
drawback of this solution. An abundance of holes must
be made into the mantle. The inner axle requires flow
ducts of its own, and suction ducts of its own.
The use of a suction box outside the mantle is
also known in conjunction with single-wire groups. An
outer face of the drying cylinder is provided with
grooves, and the negative pressure is applied to these
grooves
* - Trademark
1~38~9~
through an outside suction box placed upon the
cylinder. Thus, the negative pressure is transmitted
through the grooves to a lower face of the cylinder,
whereby a web holding force is thereby produced. This
solution requires a great deal of space and the cost of
construction is high.
The present invention is directed towards the
provision of an entirely new and improved paper machine
cylinder, which is, in particular, suitable for use in
supporting a web in conjunction with lower rolls in a
single-wire group, i.e. in a drying section of a paper
machine.
In accordance with one aspect of the present
invention, there is provided a method for guiding a web
through a group of drying cylinders having at least one
heated cylinder and having at least one leading cylinder
or roll, with the web being passed around the cylinders.
This method comprises the steps of providing the leading
cylinder or roll with holes passing through a mantle
thereof and fitting the holes in the mantle to open at
one end into an interior space within the cylinder or
roll mantle and at an opposite end into grooves provided
upon an outer face of the mantle, and applying a
negative or suction pressure to an inner face of the
mantle to generate free flow of air into the cylinder or
roll interior from an outer area surrounding the roll
mantle through the holes. Thus, the negative or suction
pressure is transmitted from
1338~97
inside the roll or cyli~der to the grooves provided in the outer
mantle ~ace, while an adhe~ion for~e iB applied to the web through
the grooves.
In particular, the group of drying cyllnder3 i~ situated ln
a multi-cylinder dry~ng ~ection of a paper machine and comprlse~ a
single-wire draw, whereby the web i8 pre~ed by a drying wire again~t
a face of the at least one heated cyl~nder, and runs outside the
drying wire about the at lea~t one leading cylinder. The at least
one heating cylinder i~ preferably heated by steam, wh~le ths drying
wir~ is preferably a felt and the leading cylinder i~ a lower
cylinder in the group of drying cylinder~.
The present invention is also dlrected to a device for
guiding a web th~ough a group of drying cylinder~ ha~ing at least one
heated cylinder and at lea~t one leading cylinder or roll, with the
web ~eing passed around the respectlve cylinders. In particular,
thi~ devlce comprises the leading cylinder or roll being provided
with holes pa~ing through a mantle thereof and being f~tted in the
~antle to open at one end into an interior ~pace within the cylinder
or roll mantle, and at an oppo~ite end into grooves provided upon an
outer face of the mantle. Mean~ are al~o pro~lded for applying
ne~atlve or suction pressure in the cylinder or roll interior, to
generate free flow of air through the holes in the mantle and into
the interior space. Thus, the negative or 6uction pressure i8
applied along an ~nner face of the cylinder or roll mantle, and is
transferred from inside the roll or cylinder to the grooves, wh~le an
adne~lon force is applied to the web through the grooves.
The group of cylinders is preferably ~ituated in a
multi-cylinder dryer section of a paper machine having a ~lngle-wire
draw in turn hav~ng a drylng wire arranged to press the we~ agalnst
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13380~
a face of the heated cylinder and to pas~ the web outside of thedrying wl~e and around the le~ding ~ylinder, while the means comprise
a cuction duct communicating with the interior of the cylinder or
roll. The at least one heated cylin~er i8 preferably heated by
steam, while the at least one leading cylinder or roll is a lower
cylin~er ln the group of dryîng cylinders, whereby the free flow of
air is generated from an upper part of th~ cylinder or rol~ and from
an area in which the wire and web are n~t pressed against the outer
mantle f ace thereof.
Furthermore, the present ~nvention is d$rected to a paper
ma~hine çylinder having shafts on which the cylinder is mounted to
revolve by means of bearing~, end flangeæ to whioh the shaf~s are
respe~tively ¢oupled, and a mantle conne~ed to the flanges at end~
thereof and having grooves on ~n outer face ~hereof. The cylinder
ha~ holes pa~cing through the mantle and opening, at one end thereo~,
into these grooves and at an oppo~ite end thereof, into an inner
space within the mantle. The groove~ are preferably fitted over
sub~tantially an entire w~dt~ of the cylinder.
The method in accordance with the present in~ention is
principally characterized by the leading cy~inder~ or rol~s bein~
provided wi~h holes pa~ing thro~gh a mantle of the leading cylinder~
or rolls, the~e holes bein~ fitted to open ~nto an interior space of
negative pre~sure in the ~e~pe~tive leadlng cylinder or roll and, at
an opposite end, to open into groove~ in the ~antle face of the
rolls. Thun, the negative prescure in~ide the roll i~ arran~ed to be
tran~mitted to the grooveq provided in the outer face of the roll
msntle, so that an adhesion force is applied to the web through the
groove~. In this method, a nega~ive p~essure is applied to th~
entire inner mantle face of the roll, while free flow of air i~
--5--
1~8097
permitted ~hrough the holes from an area, e.q., above the ~ylinder
and into the int~rior space within the cylinder.
The device in accordance with the present invention in a
drying group or groups provided wlth a sinqle-wirQ draw in a
multi-cylinder dry~r of a paper machine for Recuring the dra~ of the
we~ principally characterized by the leading cylinder bsing
provided with holes pa~slng through the mantle of the cylin~e~, thece
hole~ being fitted so that they open, at one end thereof, $nto the
grooves provided in an outer face of the mantle of the cyllnder and,
at the other end thereof, open int~ the inner spac~ of negat~ve
pressure in the cylinder. ThiC device also compri~es a source of
negative pressure, from which negative pre6~ure is applied through a
suction duct to ~he inner spa~e of negatlve pressure w~thin the
cyllnder, whereby the negative pre~ure is applied at the ~ame time
to the entire inner face of the cylinder mantle so that, from an
upper part of the cylinder, and from an area in which the wire and
the web are not pressed again~t an outer face of the cylinder, ~reo
flow of air i~ permitted through the holes in the mantle of the
cylinder and into the interior space within the cylinder.
The cyli~der in accordance with the present invention $5
principally characterized by a grooved cylind~r compri~ing a number
of holes pas~ing through a mantle and openlng, at one end, into the
grooves and openlng, at the other end, into an inner space in the
cylinder.
According to the present invention, a paper-machine cylind4r
of an entirely new type has been rormedr ~hich is e~pe~ally
well-~uited as a lower cylinder or leading roll in a slngle-wire area
in an initial part of a drying se~tion of a paper machine.
Centrifugal force and various blow phenomena attempt to detach a
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13~8~97
paper web from a wire off the face of the leadingcylinder.
In the present invention, the starting point has
been a basic fact that relatively little force is
capable of keeping the paper web upon the wire face.
According to the present invention, suction holes have
been drilled into a grooved roll, these holes passing
through the roll mantle to bottoms of grooves upon the
roll. One end or both ends of the roll is/are provided
with a shaft which comprises a suction duct, this
suction duct being further connected to a source of
suction, most appropriately to a centrifugal blower.
When the holes are appropriately dimensioned and
when the roll mantle is provided with a certain limited
number of bores that transmit the negative pressure, a
permanent negative pressure can be generated in the
interior of the roll. This negative pressure can be
maintained in spite of the fact that a part of the
holes in the roll open into the open air in the upper
part of the roll. The effect of negative pressure is
spread in the groove. In this manner, a band-shaped
force pattern that attracts the web is obtained. By
means of the negative pressure, the web is pulled
towards the roll. The suction is applied to the web
through the wire.
In accordance with a further aspect of the
invention, there is provided a paper machine cylinder,
comprising shafts on which the cylinder is mounted to
revolve by means of bearings, end flanges to which the
shafts are respectively coupled, and a mantle connected
to the flanges at ends thereof and comprising grooves
on an outer face thereof, wherein the cylinder
comprises holes passing through the mantle and opening,
at one end thereof, into the grooves and at an opposite
end thereof, into an inner space within the mantle, a
suction duct passing into the interior space of the
7a 1~380~7
cylinder or roll through which negative or suction
pressure is applied to the interior space of the roll.
The present invention will be described in greater
detail below with reference to certain preferred
embodiments illustrated in the accompanying figures,
and to which, however, the present invention is not
intended to be restricted. In the drawings,
Fig. 1 is a schematic illustration of a Sym-Press*
II press and of an initial part of a drying section in
a paper machine;
Fig. 2A illustrates a roll in accordance with the
present invention and partially illustrates the
principles of the present invention;
* - Trademark
13~8097
Fig. 2B is a sectional view along line I-I in Fig.
2A;
Fig. 3 is a graphic presentation of relationship
between negative pressure prevailing in a space of
negative pressure within a cylinder in accordance with
the present invention, and flow taking place through
holes in a mantle of the invention roll as a function of
chosen total cross-sectional flow area of these holes;
Fig. 4 is a partially sectional side view of a
cylinder in accordance with the present invention; and
Fig. 5 illustrates cross-sectional area of a hole
and cross-sectional area of a groove in accordance with
the present invention.
Fig. 1 illustrates the equipment utilized in
accordance with the present invention. The area of
single-wire draw in a multi-cylinder dryer of a paper
machine is shown in Fig. 1. The dryer comprises a line
of heated drying cylinders, preferably upper cylinders
K, as well as a line of leading cylinders or leading
rolls 10. The paper web W runs between these lines
supported by a drying wire H, e.g. a felt. The web W
runs on the heated drying cylinders K as pressed by the
drying wire H. The drying wire H presses the web W into
direct contact with the heated face of the drying
cylinder K. At the leading cylinders or lower rolls 10,
the web W runs on the outer face of the drying wire,
e.g. felt H. In such a case, in the prior art solutions
of equipment, there had been a major risk of the web W
becoming detached from the face of the leading cylinders
10.
As shown in Fig. 1, the cylinders 10 in accordance
with the present invention are situated as leading
cylinders in the single-wire group of the paper
machine. The web W is passed through the nips N1 to N3,
to a first single-felt or single-wire group.
9 13380~7
In this group, the wire H is passed over the leading
rolls lOa, lOb, and lOc. This single-felt draw, i.e.,
Uno-Run*, runs the paper web W alternatingly between
the wire H and the outer face of the drying cylinder K,
while in the case of the leading cylinders 10 of the
single-wire group, the wire H runs between the paper W
and the outer face of the cylinder 10.
As is shown in Fig. 1, the paper machine leading
cylinders lOa, lOb and lOc in accordance with the
present invention are fitted as lower cylinders of the
single-wire group. From a source 20 of negative
pressure, advantageously from a centrifugal blower,
negative pressure P1 is applied through ducts 19 into
an interior space in each of the cylinders lOa, lOb and
lOc. The source 20 of negative pressure is fitted to
be situated underneath the floor level of the paper
machine, in the basement.
Figs. 2A and 2B illustrate the principles of the
web draw and support arrangement in accordance with the
present invention. The cylinder 10 is shown as a
longitudinal sectional view in Fig. 2A. The cylinder
10 comprises a mantle 11 which is attached to the end
flanges 22 of the cylinder. The outer face lla of the
cylinder 10 mantle 11 comprises grooves 13. The
grooves 13 are closed annular grooves, which are
situated side by side in the outer face lla of the
mantle 10 and in the area of the entire mantle. The
groove 13 formation may also consist of one single
groove 13 that runs spiral-shaped. In such a case the
groove runs from one end of the mantle 10 to the other
end. The grooves 13 are preferably turned into the
mantle face, however an embodiment of the present
invention is also possible in which a band that forms
the grooves 13 is wound as spiral-shaped onto the outer
face of the mantle frame. As used herein, the term
"grooves" also refers to just a "single"
* - Trademark
133gO~7
spiral-~haped groove prepared as described above.
Negative pre6~ure Pl 1~ applied to a ~pace 14 of negative
pressure within the ~ylinder 10 from the source 2 0 of negative
pressure, e. g. from a centrifuga} ~lower. The negative pres~ure i~
tran~mitted from the ~pace 14 of negative pre~sure into the cylinder
10 through holes, preferably bore~ 15, into the groove~ 13.
rhe hole~ 15 pass perpendicularly to a central axis X-X of
the cyl$nder 10. Each hole lS opens from one of its ends into the
space 14 of negative pressure within the c:ylinder 10, and opens from
the o~her end into ;I hottnm ~6 of the gr~ve 13. The negativ~
pre~ure is transmitted through the bores 15 ~ubst~ntially across the
entire widt~ ~ of the cylinder 10.
The grooves ~ comprlse a groove ~o~om 16 ana si~ewalls
~7a, 17b. Each hole 15 opens into the g~oove ~ottom 16. The holes
15 are uniformly spaced in the groo~e 13. The cylin~r$cal space 14
of negati~e pxessure inside the cylinder mantle 1~ ubst~ntially
free from any con~tructlons or components, and the negative pre~surQ
Pl is appl$ed to th~ entire inside man~le face llb o~ the cylinder
10 .
The cylinder 10 co~prlses shafts 18 on whloh the cylinder lo
i8 rotatably journalled. At lea~t one of the shaft~ 18, the
~ervice-~ide Hp shaft as shown in Fi~. 2A, include~ a duct 18a
th~ough which negative pres~ure $s applied to the ~pace 1~ of
negative pressure situated inside the ~yl~nder 10. The service-side
shaft 18 i~ a tubular hollow 6haft and communi~ates with the suction
duo~ 1~ from the ~ource 20 of n~g~tive pre~ur~, p~r~a~ly ~rom a
centrifugal blower. Referen~e ~haracter ~ denote the driving side
of the paper machine.
Fig. 2B illustrates a ~e¢tlonal view along line I-I of Fig.
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1338097
2A. Fig. 2B also shows the runs of the paper web W and of the wire H
at a leading cylinder of a single-wire group, e.g. a single-felt
group. The cylinder 10 comprises several holes ending in the groove
13, preferably bores 15. The bores 15 are fitted as uniformly spaced
in the cylinder mantle 11. Negative pressure Pl is introduced into
the space 14 inside the cylinder 10, from the source 20 of negative
pressure, and the negative pressure is applied to prevail under all
circumstances of operation in the interior space 14 within the drying
cylinder 10. The negative pressure P1 is applied to the entire
inner face llb of the mantle 11 of the drying cylinder 10.
As shown in Fig. 2B, a holding force F is applied to the web
W, this force F causing the web W to adhere to the face of the wire H
of good permeability to air, e.g. of fabric, and thereby to the outer
face lla of the drying cylinder 10. Detachment of the web W from the
cylinder 10 is thereby prevented. As shown in Fig. 2B, the upper
face of the cylinder 10 remains free of the wire H and the web W. An
unhindered flow of air is directed through this free face into the
interior space 14 in the drying cylinder 10. The negative pressure
P1 tends to be reduced thereat. However, in accordance with the
present invention, dimensioning of the cross-sectional flow areas of
the grooves 13 and of the holes lS have been achieved so that the
negative pressure can be maintained within the interior space 14
within the cylinder 10, in spite of this free flow of air L1.
According to the present invention, the bores 15 are
dimensioned so that the desired flow of air ~ into the cylinder 10
and the desired negative pressure P1 in the interior 14 of the
cylinder 10 are achieved. A relatively low negative pressure P1 is
capable of maintainlng the web W on the face of the wire H. The
effect of this negative pressure is spread in the groove 13, and
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133~097
thereby a band-6haped force pattern ~n obtained that retains the web.
Accor~ing tb th~ pr~nt inventlon, by dlmenslonlng each
hole 15 60 tha~ its diameter ha~ a su$table dimension and provi~ing
only a certain limited number of holes lS in each groove 13, the a$r
~low ~ into t~e int~rior space 14 ~n th~ cylinder 10 is kept ~imited.
A ~er~ain holding force i8 maintained a~ the starting po$nt, this
~or~e be~ng further achieved by m~ans o~ a certaln negative pre~ure
Pl T~ n~gative pre~6urc Pl ie transferred ~hrough tne hO1~8
15 and into the grooves 13 ~itua~ed on the face lla of the cylinder
mantle 11. The ~ransfer of negative pressure Pl i~ most ef~icient
when the number o~ noles 15 is maxlmized. However~ an upper limit ~s
i~posed on the number of holes by the air flow 0 into the lnterior
~pace 14 in the cylinder 10. The desired opt~mum value i~ attained
by choosing the required negative pressure Pl and by choo~ing the
total cro~s-sectlonal flow area o~ the holes 15 such that the flow
into the interior 14 of the cylinder 10 is limited and remains within
certain low limit~, in ~pite of ~inor ~ar~tion-~ in the l~b~tive
pressure Pl.
Fig. 3 is a graphi~ presentation ln wh$ch the horizontal
coordlnates represent the negative pressure Pl inside the cylinder
10 and the verti~l coordinate~ rep~esen~ the ~low Or alr ~ lnto the
cylinder 10 through the bores 15 or equivalent. The curve~ are shown
for two ¢hosen total cross-sectional flow areas A2 and Al' of the
hole~ 15. I~ the total c~os~-sec~lonal ~low area ls large, i~e. if
the number of holes 15 ie hlgh and/or i~ the hole area is large, then
the flow passing through the holes 15 also steeply ~ncrea~e~ when ~h~
negative pressure Pl into t~e spa~e 14 is increa~ed. As abundance
of ~ir (Ll) flow6 thereat ~rom the upper slde face or the ~rying
cylinder 10 and in~o the inner space, i.e. space 14 of negative
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1338097
pre~ure within the cylinder 10. Thi~ c~se is lllustrat~d by curveA1' in Fig. 3. The curve A1' principally corresponds to the
characteristic curve of the suction roll.
To the contrary, if t~e number of holes 15 is lower andJor the
cro~s-sectional area of the~e hole~ 15 ha~ been cho~en correctly, i.e.
the total cro~-sectional flow area A~ is considerably smaller than
Al', then the form of the curve is different. In such a case, the
curve includes an almos~ horizontal part as illu6trated in Fig. 3.
Fr~m this ~llrve ~rtion it ~n h~ ~e~n that tho n4~atiue proL~ure
can be chosen within a wide ~ange of variation whil~ the flow ~,
nevertheless, remains low and within cont~olled limit~. Under these
circumstan~-es, the total number o~ the suction holes 15 ~nd their total
area mu~t be ~n a certain rela~ionship to the desired level of neqative
pressure.
For example, if the roll diameter i~ lS00 mm and the roll
length is g300 mm, and the grooves are base or width b ~ 5, height h
4, and cpacing between grooves 13 t - 20, then the total number of
grooves is 455 pcs. This value is calculated a~ follo~s. The ~idth of
the roll is ~300 ~m. The groov~s 13 are naturally located only ~n the
area where there is a paper web. In other word~ there ic a 100 mm
margln from each end face of the roll 10 to the first grocve (mo~e
s~e~i.f1~.~lly t.n thR ~Rnt.Rr of the ~roov~). Therefore, according to the
follo~ing formula
(9300 mm - ~ x 100 ~m)/t(mm) = 455 grooves,
where t = 20 mm = the spac~ng be~een the
grooves 13.
The perforation i6 carried out as follows. The number of
holes per groove is chosen a~ 30 pcs., i.e. the ~p~cing of the holes is
12, or on the face of the roll mantle about 157 mm. In the area of
threading, the holes lS are made ~nto each groove 13. The hol~s 15 are
-13-
13 3 ~ O 9 ~
made into ev~ry second groove 13 at the rear edge of thQ cyllnd~r 10,
and into every fourth groove in a middle area of the cylinder 10. The
tot~l nu~er ~f hol~ 3960 ~., wh11~ t~ di~meter ~ of each hole
15 is chosen as 4.5 mm. The total cross-~ectional area o~ the holes 15
thereat is 630 cm2. The desired negative pre&sure i8 120 mm H2O.
From the formula~
Q - ~ x Ao x v and v = ~ , the veloalty of the air
flow i5 o~ained as v = 45. 5 m/s and Q a~ Q = 2 m3/s. The fricti~nAl
resistance in the hole 15 is about 40 mm H20. In other word~, to
malntain a negative pressure of 120 mm H20, at the maximum a suction
qu~nt~ty ~f ~00 ~3 ~r ho~r ~n~ p~r m~t~r vf l~n~th of th~
roquir~d, i.e. a total of 7200 m3 per hour. It should ~e not~d that
the web W a~d the wire H part$ally sea} ~h~ roll 10, whereby the air
qU~nt ity i~ r~duc~ed and/~r the ~3uction become& deeper . Ir it i6
presumed that, in the ~uctlon ~haft 18a of th~ present example, the air
velocity is v - 3~ m/8, then the ~nner diameter of the shaft 18a i8
ob~ained as 270 mm. When ~P = 40 mm H20 i~ reserved for the
exhau6t l~sses, then ~he pressure in ~he blower i~ P - 200 mm H20 and
the power xequ~r~ment of the blower is
Q x p
Po = 102 ~kW) ~ 4 kW.
The following value~ were ufied in the accompanying formula :
g = ~ccelerntion of gr~vity
h = difference in pressure, mm H20
v = velocity m/s
~ = 1.128 kg/m3 (~40C)
Ao~ air flow area m2
- throttle factor 0.7
d = diameter of each hole
1 3 ~ ~ 0 9 7
Friction re~lstance in the hole
p - ~ . 1 . v~ ~ and
d . Z g
= 0.05 (according to Bradke), and
d - diameter of each hole
~ y means of tne example pr~sented above, it ~a~ been po~si~le
to establi~ ~he suita~ y o~ the inventlon device in practice. A
combination of a groove l~ and hole 15 pattern of low dansity i~
advantageous to manufacture, because the total nu~ber of holes 15 i~
only a ~mall portion of the corresponding number of holes in a suction
roll proper.
~ n the pre~ent invention, in at least one ~nd of the ~ylinder
10, the perforation may be made denser than in other areas of the
cylinder 10. For exa~ple, in this end o~ the cylinder 10, the
perforation ~ay be made into every groove 13, while in the other ar~as
of the cylinder l0, the perforation is not ~ade into e~ch lnd ev~ry
groove. In ~ho middle are~ o~ the cylinder 1~, th~ per~orat~on~ may be
made ~nto every ~econd or every third groove.
By the ~ame token, the internal structurea requlred by a
suction roll are co~pletely omitted in the leading cylinders 10 of the
inventlon herein. Also, in t~e absence of external box construc~ions,
the in~tial cnd of the drying ~ectlon of the paper machine can ~e
monitored and readily serviced. The masses of alr to ~e dealt with ~re
linked in the overall air-condltioning of the paper machine.
Fig. 4 illustrates a ~nstruction of a cylinder in accordance
with the present invention. The ¢ylinder 10 co~priseC a mantle 11 and
grooves 13 on the mantle ll. One groove 13 is illustrated in the
figure ~or exemplary purpo~es. The grooveQ 13 are provided
~ide-by-side acxos6 the entire ~antle face lla of the cylind~r 10. The
other grooves 13 are r~presented ln Fig. 4 by ~eans o~ dashed-dotted
lines. The negative pressure Pl i8 ~ntroduced tllrough the hollow
133~097
interior space 18a in ~he ~ha~t l~ at ~he service side ~ and ~n~o
the interior space 14 of ne~ative pres~ure within the cy~inder 10. The
shaft 18 is attached by means of screws 18' to the flange 22. ~he
shaft 18 ls fitted to revolve on bearings 21a and 21~.
Fig. 5 is a schematic reprecentation of ratio of the arsa of
the p~rforations 15 to tho ~rea of the perfor~t~ groov~ 13. The
ratio of the total cross-sectional flow area Ao of the hole~ 15 in
the cylinder to the ~otal cros~-se~tional flow area Al of the
perforated grooves 13 i5 within the range of about l:10 to 1:150, most
advantageoucly within the range o~ about 1:50 to l:llo.
Advantageously, the flow Q per meter of width of the cyl$nder
10 into the space 14 of negative P~eS3ure in the cylinder lo, i~ w$~hin
the range of a~out 500 m3/m.h. to ~500 ~3~m.h., most advantageously
within the range of abou~ 800 m3/m.h. to 1200 m3/m.h. The nogatlve
r r~?s~lr~ ~1 in th~ int-rior cps.oo 14 in thc cylind~r 10 i~
advantageously with~n the range of about 100~ Pa to 30~0 Pa. The ratio
of the total cross-~ectionAl flow area Ao of the hol~s lS to the
entire outside mantle are~ of the cylinder lO mantle ll, is wi~hln th~
ra~ge of about 1 to 2 per mill, and prefer~bly within the area of about
1.5 per mill.
The preceding de~ription of the present invention i~ merely
exemplary, and is no~ intende~ to limit the scope thereof in any way.
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